As a person extends their sailing season into Spring, Fall or Winter, if you live far enough South, you will experience condensation on the windows.  I usually sleep on the settee and don't relish getting dripped on overnight.  It took me a long time to realize where those ugly stains on my down sleeping bag came from.  I find the dew makes a mess on the acrylic when I wipe it off in the morning.  If I delay wiping, it risks staining the curtains, wall and anything below.  The alternative is to leave the forward hatch and companionway open for free ventilation, and mosquitoes, no see-ums, etc.  Ain't gonna happen to this cowboy living in Canada.  See Tech Tip C16. 

POLY - Its pretty difficult to stop condensation with only a single pane.  With the aluminum window frame it is possible to stretch thin clear poly (polyethylene) across it, apply a bit of heat from a hairdryer to shrink it wrinkle tight and voila you have a clear dual pane window that can withstand condensation.  Just DON'T touch it.  I've seen this technique used successfully in a restaurant north of the arctic circle.  All the other windows not having received this treatment were covered in 1/2" thick ice along the edge of the glass.  By the way, kids were not allowed to sit next to the windows to keep them from poking holes in the poly.  This was years ago when Saran Wrap was the only option.  Today you can buy a kit to insulate a window.

PANEL - Another solution is to cut form fitting insulated panels, placing each against the inside of the pane to block condensation.  Panels can be made from foil lined cardboard or rigid foam, each with its pros and cons.  Storage being the biggest problem.  A panel must fit snug against the inside of the aluminum frame. 

While one of these solutions will keep the windows free of condensation, you still have to maintain ventilation through the cabin if you are going to sleep onboard and the air temperature drops below the dew point.  See Tech Tip C19.